Kevin B. McCarty discovered that the feynmf.pl script creates a
temporary "properly list" file at the location "$TMPDIR/feynmf$PID.pl",
where $PID is the process ID.

Impact

A local attacker could create symbolic links in the directory where the
temporary files are written, pointing to a valid file somewhere on the
filesystem that is writable by the user running Feynmf. When Feynmf
writes the temporary file, the target valid file would then be
overwritten with the contents of the Feynmf temporary file.